1. Field of the Invention
The present invention relates to a hydrodynamic coupling device, in particular a torque converter. The interior of the hydrodynamic coupling device may be separated into a first fluid space and a second fluid space by means of a clutch element comprising a lockup clutch and a friction surface arrangement. The clutch element is capable of being pressed up to a housing or a component connected to the housing, with the friction surface arrangement interposed. In the friction surface arrangement is a fluid duct arrangement, into which working fluid can flow from the first fluid space and out of which working fluid can flow only toward the first fluid space. Working fluid is supplied to the first fluid space by means of a first connecting duct arrangement and working fluid is led into and/or out of the second fluid space by means of a second connecting duct arrangement.
2. Description of the Related Art
A hydrodynamic coupling device is known from EP 0 428 248 A1. The lockup clutch of this coupling device, designed as a hydrodynamic torque converter has, a clutch piston which is capable of being pressed in the radially outer region against a housing cover. A ring-like friction lining is interposed as a friction surface arrangement. Provided in the ring-like friction lining are axially continuous fluid flow ducts which extend radially outward at an angle. Working fluid can flow out of a fluid space of the torque converter into the axially continuous fluid flow ducts through a passage orifice in the piston and is then discharged radially outward again into a region of the same fluid space. Cooling of the friction lining in the traction slip mode is thereby ensured by means of a flow generated by interaction of centrifugal force effects and shear fluid effects. At the same time, care is taken to ensure that no working fluid cooling the friction lining can flow into a fluid space formed between the piston and the housing cover, so that the coupling efficiency of the lockup clutch is not impaired.
An embodiment of this type has proved advantageous in terms of maintaining a high degree of coupling efficiency of the lockup clutch. However, the problem with this arrangement is that the working fluid flowing into the same fluid space again does not participate in an overall fluid exchange. Therefore, various structural measures, for example external cooling by means of cooling ribs or the like, must be taken to ensure that the entire torque converter does not gradually heat up.
The object of the present invention is to develop a generic hydrodynamic coupling device in such a way that, along with a high degree of coupling efficiency, good cooling of the entire system is ensured.
The present invention is a hydrodynamic coupling device including a housing, a lock up clutch, a friction surface mechanism, a fluid duct means and three connecting duct means. The lock up clutch has a clutch element arranged in the housing and may be pressed toward the housing. The friction surface mechanism is arranged between the clutch element and the housing. The clutch element and the friction surface mechanism separate an interior of the hydrodynamic coupling device into a first fluid space and a second fluid space. The fluid duct means is in the friction surface mechanism and permits the working fluid to flow into and out of the first fluid space while preventing the working fluid from flowing out of the first fluid space into the second fluid space. The connecting duct means are in the fluid duct means, with the first connecting duct means being capable of permitting flow of the working fluid to the first fluid space, and the second connecting duct means being capable of permitting flow of the working fluid into and out of the second fluid space. The third connecting duct means is capable of circulating the working fluid within the first fluid space before permitting the working fluid to flow out of the first fluid space, at least when the clutch element is pressed up toward the housing with the friction surface arrangement interposed between them.
The present invention ensures that, even though the cooling flow over the friction surface arrangement is generated solely as a result of the inclusion of the first fluid space, the heated working fluid can flow out of the interior at least partially and can be replaced by colder working fluid. Even in a lengthy traction slip mode, in which fluid exchange is otherwise not ensured due to the fluid pressure being maintained in the interior of the coupling device, cooling is achieved.
For example, a turbine wheel may be arranged rotatably about an axis of rotation in the first fluid space. The first connecting duct arrangement and the third connecting duct arrangement may be connected to the first fluid space on axial sides of the turbine wheel, in particular of a turbine wheel shell. The axial sides of the turbine wheel are opposite one another with respect to the axis of rotation. Preferably, the third connecting duct arrangement is connected to the first fluid space in a region between the turbine wheel (in particular a turbine wheel shell) and the clutch element (or clutch piston). As a result, working fluid that has flowed into the first fluid space cannot immediately flow out of the first fluid space again through the third connecting duct arrangement, without having participated at least partially in a circulating action.
The third connecting duct arrangement in a turbine wheel hub may comprise at least one first fluid passage orifice extending essentially radially. An output shaft may be provided so that fluid can be supplied in a simple way to the second fluid space and fluid can be discharged from the latter. The output shaft has a second fluid passage orifice which extends essentially in the direction of an axis of rotation and which forms at least part of the second connecting duct arrangement.
To obtain a very simple design, in which three completely separately activatable connecting duct arrangements do not have to be provided, i.e. in a 3-line system, the second connecting duct arrangement and the third connecting duct arrangement are connected to one another in a radially inner region. For example, this may be achieved by opening the third connecting duct arrangement into the second fluid passage orifice.
At least one passage orifice for leading working fluid into the fluid duct arrangement may be provided in the clutch element. Preferably, at least one outflow orifice for leading working fluid out of the fluid duct arrangement into the first fluid space is provided in the clutch element. Thus, the working fluid also flows into the first fluid space again in the region, or at the side of the clutch element, out of which it previously flowed into the fluid duct arrangement. This is advantageous, in particular, when this region of the first fluid space is also in fluid exchange connection with the third connecting duct arrangement.
In order to use the shear effects or frictional effects occurring during the flow through the fluid duct arrangement, an inflow orifice and an outflow orifice, which are assigned to the same fluid duct portion of the fluid duct arrangement, are offset relative to one another in the circumferential direction. Preferably, the friction surface arrangement is movable in the circumferential direction with respect to at least one subassembly of clutch element and housing or to a component connected to it, while the fluid duct arrangement comprises a groove-like duct arrangement which is open on a friction surface of the friction surface arrangement, the friction surface interacting with the at least one subassembly.
The shear or friction action may be utilized with the greatest possible efficiency if the fluid duct arrangement comprises at least one fluid duct region which extends essentially only in the circumferential direction.
The present invention further relates to a friction surface arrangement for a hydrodynamic coupling device, in which the friction surface arrangement is provided with a fluid duct arrangement, in which working fluid can flow in or out of a fluid space and can flow out only to the same fluid space.
According to the present invention, in this friction surface arrangement, the fluid duct arrangement is designed, at least in regions, to extend essentially only in the circumferential direction, and/or for the fluid duct arrangement to be closed off against the passage of fluid in an outer circumferential surface region and an inner circumferential surface region of the friction surface arrangement.
Furthermore, the friction surface arrangement may be designed so that the fluid duct arrangement has at least one inflow region, in which working fluid can flow in through a clutch element of a lockup clutch of the hydrodynamic coupling device and has at least one outflow region. Working fluid can flow out of the out flow region through the clutch element. As stated previously, the advantage of an arrangement of this type is that the working fluid leaving the fluid duct arrangement can then flow very quickly to a connecting duct arrangement leading this working fluid having relatively high temperature out of the interior of the coupling device.
According to a further embodiment of the present invention, a friction surface arrangement, has a fluid duct arrangement, into which working fluid can flow out of a fluid space and can flow out only to the same fluid space. At the same time, according to the invention, the fluid duct arrangement has at least one fluid duct with a first end region and with a second end region. The fluid duct is open at both regions to a radial end region, preferably a radially outer region, of the friction surface arrangement. In this embodiment both end regions of a fluid duct are open toward the same radial end region, so that fluid exchange with the same fluid space can take place in a simple way.
At the same time, at least one fluid duct may be designed essentially symmetrically with respect to a radial line. For example, it is possible for the at least one fluid duct to extend essentially rectilinearly. To enable as large a surface or volume region of the friction surface arrangement as possible to be cooled by cooling medium, the at least one fluid duct may have a region of curvature between its end regions. At the same time, it is also possible for the at least one fluid duct to run essentially rectilinearly in its end regions.
Along with a relatively high stability of the friction surface arrangement, it is possible to ensure uniform cooling over the entire surface, by the fluid duct arrangement having at least two fluid ducts arranged so as to be radially staggered. The end regions of one of the at least two fluid ducts being open to the radial end region of the friction surface arrangement in the circumferential direction between the end regions of the other of the at least two fluid ducts. Preferably, the end regions of one of the at least two fluid ducts form an opening angle in the range of 60xc2x0-70xc2x0, more preferably approximately 65xc2x0. Preferably, the end regions of another of the at least two fluid ducts form an opening angle in the range of 65xc2x0-75xc2x0, preferably approximately 70xc2x0. In order to avoid an accumulation of fluid in the region of curvature, i.e. to make the flow resistance as low as possible, one of the at least two fluid ducts may have in its region of curvature a radius of curvature in the range of 6-8 cm, preferably approximately 6.8 cm. Preferably, another of the at least two fluid ducts may have in its region of curvature a radius of curvature in the range of 12-14 cm, preferably approximately 12.8 cm.
According to an alternative, highly advantageous embodiment, at least one fluid duct may have a central region extending essentially in the circumferential direction and, adjoining the central region, respective regions of curvature. The result of providing an essentially circumferentially extending central region of the at least one fluid duct is that, highly effective forward transport of the fluid located in the duct occurs due to shear action. In an embodiment of this type, at least one of the regions of curvature has adjoining it a duct portion extending essentially rectilinearly and forming one of the first and second end regions. Alternatively or additionally, it is possible for at least one of the regions of curvature to form one of the first and second end regions.
In order to obtain a stable configuration in an embodiment of this type, too, or to eliminate, as far as possible, the risk of various material regions breaking away the first and/or the second end region of the at least one fluid duct form an angle in the range of 40xc2x0-60xc2x0, preferably approximately 50xc2x0, with respect to a tangential line and/or have a radius of curvature in the range of 12-23 cm, preferably approximately 17.5 cm in at least one region of curvature.
According to a preferred embodiment, the at least one fluid duct is curved radially outward near one of its end regions. The result of this is that, the fluid arranged in the radially outwardly curved end region is drawn outward by virtue of the centrifugal forces occurring during rotational operation, ensuring a throughflow in a defined way.
It is also advantageous, to have as uniform a heat discharge as possible, if at least two fluid ducts are connected to one another by means of a connecting duct arrangement.
In order to obtain a uniform cooling action over the entire surface region, the fluid duct arrangement has a plurality of fluid ducts succeeding one another in the circumferential direction.
Furthermore, in the friction surface arrangement according to the present invention, preferably the plurality of fluid ducts comprise a plurality of fluid duct groups where spacing between the fluid ducts in a fluid duct group is smaller than spacing between individual fluid duct groups. Division into individual fluid duct groups has the advantage of producing, between the individual groups, larger free regions through which ducts do not pass and in which so-called lining locks of individual lining segments may be placed. As a result, a complete annular friction lining can, for example, be assembled from a plurality of identically shaped lining segments.
For manufacturing purposes, it is also advantageous if at least one fluid duct is open, in its first and second end region, to a radially inner end region of the friction surface arrangement. In an arrangement of this kind, at least one radially inwardly open fluid duct can be produced by the stamping method and extend through the entire material thickness of a friction lining. A friction ring portion may be provided to adjoin the inner end region of the duct radially on the inside. When a friction lining of this type is being glued to a friction lining carrier, it initially also holds together various portions of the friction lining and, after gluing, is then stamped off, to produce material regions completely separate from one another.
According to a further embodiment of the present invention, a friction surface arrangement has a fluid duct arrangement, into which working fluid can flow from a fluid space and can flow out only to the same fluid space.
At the same time, the friction surface arrangement has a friction surface carrier and a friction surface clement on each side of the carrier. A first fluid duct arrangement region is arranged in a first of the friction surface elements and a second fluid duct arrangement region is arranged in a second of the friction surface elements. A connecting orifice arrangement is provided in the friction surface carrier via which the first fluid duct arrangement region and the second fluid duct arrangement region are in fluid exchange connection.
An arrangement is thus produced in which at least two friction surface pairings rub against one another so that, while the pressing force remains the same, the entire friction surface can be increased and therefore the torque transmission capacity can be increased.
In this embodiment, too, preferably the first fluid duct arrangement region and the second fluid duct arrangement region are open to a radial end region, preferably a radially outer region, of the first friction surface element and of the second friction surface element respectively. The first fluid duct arrangement region and the second fluid duct arrangement region each have at least one fluid duct which, in one end region, is open to the radial end region of the respective friction surface element and is connected to the other fluid duct arrangement at another end region.
To simplify assembly in the embodiment in which the friction surface arrangement has two friction surface elements or to minimize the work necessary for aligning specific orifices serving for the passage of fluid, at least one of the fluid duct arrangement regions has at least one ring-like connecting orifice arrangement, into which the connecting orifice arrangement opens. Preferably, the at least one fluid duct opens with its other end region into the connecting duct arrangement.
In order to provide an arrangement in which pressure conditions prevailing in different radial regions can be utilized, one of the fluid duct arrangement regions is open on a radial end region, preferably a radially outer region, of the associated friction surface element. The other fluid duct arrangement region is in or capable of being brought into fluid exchange connection with the fluid space via a further connecting orifice arrangement in a clutch element of a lockup clutch arrangement. In this case, the clutch arrangement is capable of being brought into frictional engagement with the friction surface element.
In this embodiment, too, preferably one fluid duct arrangement region has at least one fluid duct which, in one end region, is open to the radially outer end region of the associated friction surface element and, via its other end region, is connected to the other fluid duct arrangement region. The other fluid duct arrangement region then has a ring-like connecting duct arrangement, into which the connecting orifice arrangement and/or the further connecting orifice arrangement opens.
To ensure that cooling fluid flows through the fluid duct arrangement regions before it flows out through the further connecting orifice arrangement, in an embodiment of the present invention, the connecting orifice arrangement and the further connecting orifice arrangement each have at least one fluid passage connecting orifice. The number of fluid passage connecting orifices of the connecting orifice arrangement differs from the number of fluid passage connecting orifices of the further connecting arrangement. Therefore, in any relative rotary position, the fluid passage connecting orifices of the connecting orifice arrangement will not be aligned with the fluid passage orifices of the further connecting orifice arrangement so that the fluid will not be fed into the fluid space again directly without flowing into further duct regions.
In the friction surface arrangement according to the present invention, preferably the fluid duct arrangement has a cross-sectional profile narrowing toward a duct bottom in at least one length region. The result of an arrangement of this type is to reduce drag torque. For example, when the lockup clutch is disengaged, the drag torque with which a friction lining bearing against a rotating component is taken up, is reduced, since, due to a narrowing duct geometry, fluid is forced in the manner of a nozzle or wedge between the lining and the rotating component and thus contributes to lifting off the lining. At the same time, it is possible for the narrowing cross-sectional profile to be formed by duct walls extending essentially rectilinearly toward the duct bottom. In addition, at least one duct wall delimiting the fluid duct wall can merge, in a region of curvature, into a friction surface region of the friction surface arrangement.
The present invention relates, furthermore, to a hydrodynamic coupling device, in particular a hydrodynamic torque converter or fluid clutch, with a friction surface arrangement or friction element having a friction lining carrier of approximately ring-like shape with a friction surface arrangement on at least one side of the friction lining carrier.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.